4G networks are the fourth generation of mobile telecommunication technology standards, and include the WiMAX and LTE-Advanced network standards. The 4G networks include a new architecture to support a small-scale basestation, which may be installed in private homes (known as a femto access point, or femtocell), or outdoor areas (known as metrocells or picocells, depending on the coverage area). These cells are collectively known as small cells.
Small cells are expected to be widely adopted. However, as small cells are designed to be deployed by end-users with minimal intervention from Mobile Network Operators, MNOs, several issues arise. For example, if two small cells have overlapping coverage areas (as shown in FIG. 1, and hereinafter known as “neighboring small cells”) but transmit using the same frequency and time slots, then signals from these two neighboring small cells will interfere with each other and data throughput is significantly reduced. This form of interference is known as co-tier, as the interference is between two elements on the same tier of the network. There may also be interference between signals from the macrocell and small cell when they use the same frequency and time slots, known as cross-tier interference. To address these issues and minimize interference in the network, MNOs employ various resource management techniques.
A first technique involves the MNO using a centralized resource management node to allocate resource blocks (i.e. a resource unit discretized in frequency/time slot space) to each small cell in the network. The centralized node is able to determine the resource requirements of each small cell and then allocate resources in an equitable manner. Examples of centralized resource management nodes can be found in “Resource Allocation with Interference Avoidance in OFDMA Femtocell Networks”, Liang et al, IEEE Transactions on Vehicular Technology, June 2012, and in International Patent Application Publication No. 2012/139653. However, as the size of the small cell network increases, there is a corresponding increase in control traffic. This solution is therefore not ideal, as small cell systems are expected to be widely adopted.
An alternative solution is a distributed approach to resource allocation, such that each small cell independently determines its own resource allocation. This may involve the small cell determining the resource requirements of its neighboring small cells, before calculating its own resource allocation based on an algorithm. This has the benefit of reducing the amount of control traffic on the network compared to the centralized node approach above, but the resource allocation tends to be too conservative using this technique (as avoiding interference is more preferable to MNOs than maximizing throughput).
Chinese patent application publication number 103379498 A discloses a resource allocation method in which in which a first basestation determines its spectrum utilization information and sends it to a second basestation. The second basestation then allocates a spare resource either to itself or to the first basestation based on this information. This is a form of distributed resource allocation, but with some control information passing between basestations.
It is therefore desirable to alleviate some or all of the above problems.